Le Chatlier's Principle

Question 1

In a reaction, if you increase the pressure or decrease volume, the rxn will move toward the side with more or less moles?

Answer 1

Less moles. By increasing the pressure, the rxn will want to balance out and this can be achieved by heading in the direction of the rxn that has less moles.

Question 2

In a reaction, if you decrease the pressure or increase the volume of one side, will the reaction move toward the side with more or less moles of gas?

Answer 2

It would move toward the side with more moles to compensate.

Question 3

Changes in temperature, if you increase the temperature , the reaction will move toward what side ?

Answer 3

The reaction will favor the side in which heat is not a part of.

Question 4

If you decrease the temperature of a reaction, what side will the reaction move toward?

Answer 4

It will favor the side of the reaction that generates heat to compensate

Question 5

If reactants are added or products are removed

Answer 5

Q

Question 6

If reactants are removed or products are added

Answer 6

Q > Keq

Question 7

Enthalpy

Answer 7

Heat changes at constant pressure. It is a state function. All we need to do is compare the final and initial state. A positive dH value is endothermpic (breaking bonds). -dH means reaction is exothermic (Forming bonds)

Question 8

You cannot determine spontaneity from

Answer 8

Enthalpy. You can determine it from Gibbs Free Energy ONLY!

Question 9

Standard Enthalpy (Heat) of Formation

Answer 9

Enthalpy requuired to produce one mole of a compound from its elements in their standard states. 298 K or 25 Celcius and 1 atm. Do not assume standard state is a common state.

Question 10

Standard Heat of Reaction:

Answer 10

This is a state function, so subtract - final- initial. Only can do this if we know what the heat of formation of the compounds are.

Question 11

Hess’s Law

Answer 11

States that enthalpy of a reaction is a sum of each reaction. Basically say that there are several intermediates, but if we add the steps together we can get the total. It applies really to all of the state functions.

Question 12

Bond Dissociation Energy

Answer 12

Average energy required to break a bond, expect the units to be in kJ/mol. All bond dissociation energies are endothermic. If we use this we just take the total enthalpy of bonds broken- bonds formed. You can look at this as total energy absorbed - total energy released. This breaks the general trend because it is going from initial-final and not final- initial.

Question 13

The heat of combustion will always have a - or + dH rxn?

Answer 13

-dH rxn

Question 14

A positive H is

Answer 14

endothermic

Question 15

A negative H is

Answer 15

exothermic

Question 16

The Second Law of Thermodynamics deals with

Answer 16

Entropy. Work must be applied for energy to move from a diffuse to a more localized state.

Question 17

Entropy

Answer 17

Measure of spontaneious disperal of energy at a specific temperature. dS= Q(heat gained or lost)/ T ( in Kelvin). Heat energy into a system (entropy increases). If we take heat energy out of a system (entropy decreases).

Question 18

Entropy Equations

Answer 18

Entropy universe= Entropy of system + Energy of surroundings >0

Standard Entropy (state function, pathway independent, final and initial state is all that matters)
dS rxn = Summ of dS products - dS reactants

Question 19

By decreasing activation energy of the reaction , what effect is produced on equilibrium constant?

Answer 19

nothing it stays constant. Only temperature can change the equilibrium constant

Question 20

State functions

Answer 20

gibbs, entropy , enthalpy and volume change

Question 21

catalyst

Answer 21

decreases activation energy AND is regenerated

Question 22

Grahams Law

Answer 22

Kinetic Energy of Ideal Gases= 3/2nRT. It means that gases at the same temperature have the same kinetic energy.

Question 23

Ideal Behavior Includes

Answer 23

No intermolecular forces, No volume of particles